Electronic vapor provision systems such as e-cigarettes generally contain a reservoir of liquid, typically nicotine, which is to be vaporized or otherwise converted into an aerosol. Such devices are usually provided with one or more air inlet holes located away from the mouthpiece. When a user sucks on the mouthpiece, air is drawn in through the inlet holes and past the vapor source, such as a heater supplied with nicotine or other liquid from a cartridge.
Some e-cigarettes are provided with a specific manual activation facility, such as a button which is used to activate the heater. In such devices, the heater is only activated while the user is holding down the button. However, such a manual activation facility may be activated accidently, for example, if something presses against the button while the device is located in a user's pocket. This can then cause the heater to become activated unintentionally, often without the user's knowledge, which will generally waste battery power, and may also cause damage to the heater and/or injury to the user.
An existing solution to such a problem is to providing such devices with a more complex activation mechanism so that it is difficult to activate accidently. For example, a device may have a button which requires a certain number of consecutive presses by the user in order for activation of the heater to occur. However, such relatively complicated mechanisms are generally more inconvenient and cumbersome for a user.
Another approach adopted by some devices for avoiding accidental activation is to have the heater activated automatically by an airflow sensor (such as a pressure drop sensor) which detects airflow through the device as the user inhales on the device. More particularly, when a user inhales on the device, the heater is activated to vaporize a small amount of liquid, which is therefore inhaled by the user. However, this allows the heater (and hence the e-cigarette) to be activated by someone other than an intended user, who picks up the e-cigarette and mimics the action of inhalation.
The approach described herein seeks to help address the above-mentioned problems.